Investigation on influences of polymer solution properties on stress distribution and deformation of residual oil

After water flooding, there is much residual oil left in the pores. This cannot be easily displaced, but polymer flooding is able to achieve this. The use of viscoelastic solutions such as polymer can enhance the oil recovery, because it can increase the sweep volume by improving the mobility ratio of polymer solution and oil. The use of viscoelastic solutions can also increase the displacement efficiency of residual oil in the swept area. This article, based on the momentum equation and Oldroyd-B constitutive model, investigates the influences of polymer solution properties on the stress distribution and deformation of residual oil adhering to the walls of micro-channels. The results show that the elasticity and viscosity of the polymer displacing fluid are the factors with the greatest impact on the stress distribution and deformation of residual oil. The stress computation shows that along the direction of flow, the oil film is compressed at both ends, and pulled in the center. This stress distribution helps the oil film to bulge from its center, leading to its deformation and break-up. Furthermore, by increasing the viscosity or elasticity the residual oil is exposed to greater stress and deformation during the displacement process, which is characterized by a large advancing angle, an increasing deformation index and a small receding angle. Comparison of the simulation and experimental results shows a good conformance. Therefore, to displace the oil more efficiently, the polymer solutions need to be more viscous and elastic, which can be achieved by changing their chemical properties. The results clarify the micro-mechanism of polymers displacing residual oil and quantify the influences of the chemical properties of the solution on the stress, deformation and activation of residual oil.